Abstract
3-Alkoxycarbonylmethyl-6-bromo- and 3-alkoxycarbonylmethyl-6-nitro-2-benzothiazolones were synthesized by reaction of alkylesters of halogenoacetic acids with 6-bromo-2-benzothiazolones and 6-nitro-2-benzothiazolones respectively. The compounds were tested for plant growth stimulating activity on wheat (Triticum aestivum). The bromo derivatives manifested 25.4 % average stimulating activity in comparison with the control. The stimulation activity of the nitro derivatives was not significant. Optimal structures of the compounds were obtained by a MMPI method, atomic charges and dipole moments were calculated by a semiempirical AM1 method. On the basis of molecular electrostatic potential it has been found that the biological activity of synthesized compounds depends on charge distribution in the molecules.
Highlights
Good plant growth stimulating activity of benzothiazole derivatives [1,2,3,4,5,6,7,8,9,10,11,12,13] has been a challenge for synthesis of further compounds of this type. 4-Chloro-3-(3-oxa-5-pentenyloxycarbonylmethyl)-2benzothiazolone [16] has been found to manifest 68 % activity of stimulation in comparison with the control, which is 17 % higher than the activity of 2,4-dichlorophenoxyacetic acid used as standard. 3Phenoxycarbonylmethyl-2-benzothiazolone showed 32.7 % activity [13], but its 4-chloro derivative manifested 60 % efficiency [13]
The average stimulating activity in comparison to the control was 25.43 % for the bromo derivatives and only 5.53% for the nitro derivatives, which is near to the range of experimental error
The synthesized compounds were studied from the viewpoint of influence of bromo and nitro substituents upon their plant growth stimulating activity
Summary
Good plant growth stimulating activity of benzothiazole derivatives [1,2,3,4,5,6,7,8,9,10,11,12,13] has been a challenge for synthesis of further compounds of this type. 4-Chloro-3-(3-oxa-5-pentenyloxycarbonylmethyl)-2benzothiazolone [16] has been found to manifest 68 % activity of stimulation in comparison with the control, which is 17 % higher than the activity of 2,4-dichlorophenoxyacetic acid used as standard. 3Phenoxycarbonylmethyl-2-benzothiazolone showed 32.7 % activity [13], but its 4-chloro derivative manifested 60 % efficiency [13]. Good plant growth stimulating activity of benzothiazole derivatives [1,2,3,4,5,6,7,8,9,10,11,12,13] has been a challenge for synthesis of further compounds of this type. 4-Chloro-3-(3-oxa-5-pentenyloxycarbonylmethyl)-2benzothiazolone [16] has been found to manifest 68 % activity of stimulation in comparison with the control, which is 17 % higher than the activity of 2,4-dichlorophenoxyacetic acid used as standard.
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